Controle biológico do crestamento bacteriano comum e da antracnose em folhas de feijão pela pulverização de bactérias.

Abstract

Brazil is a great producer of beans, although their productivity is low. This occurs mainly by the incidence of diseases such as bacterial bean common blight (Xanthomonas axonopodis pv. phaseoli) (Xap) and anthracnose (Colletotrichum lindemuthianum) that can reduce the production up to 60% under favorable conditions. Control methods that reduce production costs and environmental damage appear as an effective alternative, as is the case of biological control. So, the objective of this work was to evaluate the potential of preselected bacteria to control common bacterial blight and anthracnose. These bacteria were isolated from different habitats, and previously selected through for Xap biocontrol using seeds microbiolization. They were tested in greenhouse by spraying bacterial suspensions in bean leaves. The eleven treatments used were compounds by bacteria individually (DFs093 Bacillus cereus; DFs513 Pseudomonas veronii; DFs769 Bacillus cereus; DFs831 Pseudomonas fluorescens; DFs842 Pseudomonas fluorescens; DFs843 Rhodococcus fascians; DFs912 Rhodococcus fascians) or their combination (C01=DFs093/769/831; C02=DFs093/769/842; C03=DFs769/348/831) and the check (NaCl 0,85%), applied in four different times: 24 hours before (Assay I) and after (Assay II) the pathogen inoculation; and 48 hours before (Assay III), and after (Assay IV). Additionally, the bacteria were tested in vitro for their ability to inhibit the growth of those pathogens by the production of volatile or non-volatile antimicrobial compounds. Generally, for assays with Xap, spraying DFs513 and combinations C01 and C03 reduced the severity and incidence of bacterial common blight when they were applied 48 hours after pathogen inoculation. Furthermore, most of the isolates produced antimicrobial compounds volatile or non-volatile against Xap in vitro. In assays relating to anthracnose, the isolated DFs513 and C01 combination reduced the severity and incidence in Assay II. Furthermore, DFs093 and DFs769 showed lower severity in Assay I. All isolates tested in vitro were able to inhibit the mycelial growth of the pathogen. Thus, it is observed that bacteria from different habitats and preselected for microbiolization seeds, have potential to control X. axonopodis pv. phaseoli and/ or C. lindemuthianum when sprayed on the phylloplane of beans, and that the combination C01 and isolated DFs513 have broader spectrum of action, reducing the severity and incidence of the two diseases.